Hey Lem,
Well because I am already in "ALT HLD". Any time you level off with the MCP with a set altitude lower than you set cruise alt the aircraft goes FMC SPD/ALT HLD. In this particular case the window will stay blank, why it does not go MCP SPD insted of FMC SPD is beyond me, I guess it has really not left VNAV, that's why I call it limbo VNAV
, regardless I will have to dial in a higher alt and engage VNAV to get climbing again. Just had me wondering the procedure for changing speed here ...